It is 1911.

Returning to Britain from Africa, Erasmus and Roka find themselves thrown into a perilous sequence of chase, capture and escape. Yet they must return to Sheffield as fast as they can, and in secret, there to prepare for an inevitable confrontation inside Sir Tantalus Blackmore's Factory.

But it is not only Sir Tantalus whom they must face. As the British Army, automaton horrors, and a band of desperate Marxist engineers converge around the Factory, Erasmus and Roka must decide who to trust and who to work with...

Can they overcome the fiendishly complex defences of the Factory? Will the diabolical agents of the Clockwork Garden stop them, or will Sir Tantalus himself step in? Who, in the end, will reach the heart of the Factory to learn its terrible secrets?

The final part of a breathtaking adventure through an alternative Edwardian Britain and beyond, where clockwork automata and their makers threaten to change the world forever.